The hickory handles are custom made by a Mennonite wheelwright shop in Ontario, Canada -- the family-operated enterprise that also makes our adjustable snaths.
As is the case with most hoe handles around the world, these (much like a pick ax) are friction fitted - they slide in from the top of the tapered eye. Because the protruding "top" of the handle is larger than top end of the eye, no wedge is necessary; the head can never fly off during work, yet it can be removed in a matter of seconds (for seasonal oiling of the wood within the eye, or replacement of the handle). It is also infinitely easier to self- make a handle of this kind than for the "tang & ferule" style of attachment typically used on North American hoes.
On this note, we'd like to encourage folks to make their own handles - because doing so will eventually take you to yet another level of tool appreciation. Besides, learning more practical self-reliant skills is soon to become a major new trend...